Append new log entries to a file

[bergie]

Uses Mustache templating to allow customisation. Fixes #42

$ touch /tmp/print  
$ tail -f /tmp/print
2023-04-27|08:37|60°5′4″N|23°32′20″E|0|42|13.8||1016.06|Hello, world!
2023-04-27|08:39|60°4′43″N|23°31′55″E|0.1|207|14.3||1016.09|Second entry

[thesailingengineer]

This is honestly amazing - and you've done it with so few lines of code! a few development ideas:

• can a 'start' line be added so that the headings can be printed before the line by line is started? also, maybe the date and crew before the headings?
• also, can the lat and long use simple text? Not all line printers support Unicode by default and would need more complex code to be sent to them (it's not too hard, but would be different for each type of printer.
• is it possible to change the record interval to 15min or 30 min? This makes testing a little easier! Thank you so much!

[bergie]

It might be best to decouple this functionality to a separate Signal K plugin. We need #53 to enable that.

Then we could maybe even implement nicer formatting etc as supported by Esc/POS printers.